TBH the Honda filter is bloody good, I had a Pipercross filter with Akra slip on and I noticed no real diference after mapping, I would put the money to better use if it was me
Yep with O2 eliminator (comes with PCV) you will see a vast improvement, especially after a custom map, very smooth with no flat spots
are you planning to fit the PCV yourself or get it fitted ? Generally there are specialist dynojet centres to do the mapping for you, MK dyno are closest to you, give them a ring and see what they can do for you, a custom session is about £150 usually http://www.dynojet.co.uk/index.php/atcs?detail=true&dealerid=236
The differance between the 2 is how well they perform. the road version will filter the air much better but will be restrictive and not let the air flow as well the race version will be a much less dense filter so the air will flow through much faster and create more power but not at great idea on the road as it can let more dirt into the engine which obviously not good